Health Data Research UK (HDR UK) believes that Trusted Research Environments (TREs) are a key enabler to unlocking this potential. This talk will highlight the opportunities and challenges of building a resilient network of TREs to provide holistic and secure access to patient data across spatial, temporal and multi-modal scales; including the potential to link and augment this with related datasets, such as social and environmental determinants of health (what we have termed “FOREST” – Federated, Open, Resilient, Ecosystem of Secure TREs). While “interoperability” might not be sexy, this session will set out why it is crucial to realise the true ambition of TREs.